1. Field of the Invention
The present invention relates to a non-destructive examination device for examining fatigue or state of breaking of structure such as architectures, bridges, and machines called as "examination targets" to use an elastic wave, for example.
2. Description of the Prior Art
A vibration examination is an important technology for a structure design, where the vibration examination examines the states of fatigue and breaking of the examination target and estimates mechanical strength of them in order to design an optimum structure thereof.
A main object of the vibration examination is to identify a dynamic character and a vibration mode of an examination target. The non-destructive examination device used for the vibration examination generates a vibration and provides the generated vibration to the target to vibrate it. It then measures the response information of the magnitude of the generated vibration in the examination target, echo transmitted from the examination target, and a vibration state of the examination target. Then, it processes the response information as measured results and obtain required information of the examination target.
There are conventional methods in the prior art to provide the vibration to the examination target, for example a vibration exciter device as a first method, and an impact hammer as a second method which have been described in a literature, "MODE ANALYSIS INTRODUCTION", NAGAMATU AKIO, pages 221-228, CORONA publishing CO., LTD.
There are mechanical vibration exciter devices such as an electrical type oil hydraulic vibration exciter device, a piezo electric vibration exciter device, and a conductive vibration exciter device. The mechanical vibration exciter devices use an internal force as a drive force generated by mechanical motion. The electrical type oil hydraulic vibration exciter has oil hydraulic cylinders and oil hydraulic valves whose opening and closing are controlled electrically in order to move the oil hydraulic cylinders. The piezo electric vibration exciter utilizes a piezo electricity effect. The conductive vibration exciter utilizes Lorentz's force acting on a current in a magnetic field.
However, to use these conventional vibration exciter devices, they must be attached on an examination target to examine it and the examination target must be processed in order to attach the vibration exciter device. These methods lack application flexibility. In addition, the mass of the vibration exciter device to be attached on the examination target affects the dynamic characteristics of the examination target. This is unavoidable. This is a problem.
An impact hammer is widely used for vibrating an examination target.
FIG. 1 illustrates a block configuration diagram of a conventional non-destructive examination device using an impact hammer which has been disclosed in the previous literature.
In FIG. 1, a reference number 1 designates an impact hammer, 2 denotes a examination target to be examined, 3 denotes a response detector device, 4 denotes an amplifier for amplifying an output signal transmitted from the response detector device 3, and 5 designates a signal processing device for extracting and selecting required examination data by processing the amplified output signal form the amplifier 4.
Next, the operation of the conventional non-destructive vibration exciter device shown in FIG. 1 will now be explained.
A vibrational response generated in the examination target which has been vibrated by the impact hammer 1 is detected and converted to an electric signal by the response detector device such as an acceleration sensor. The converted electric signal is amplified by the amplifier 4 and then transferred to the signal processing device 5. In the signal processing device 5, the electric signal received is processed using processes such as a high speed Fourier transformation process, or an integral process. Then, the evaluation or estimation of the state of the examination target 2 is performed based on the result obtained by the above processes.
An operator performs the addition of the vibration to the examination target 2 by using the impact hammer 1. Because an impact operation time period in which the operator adds the vibration to the examination target 2 by using the impact hammer 1 is short and the operator can perform it relatively easy, it is widely used to evaluate the state of the examination target 2. However, it is required for the operator to have a high skill level and a highly technical background in order to use the conventional non-destructive examination device shown in FIG. 1.